Controlled synthesis of AgNPs@ZIF-8 composite: Efficient heterogeneous photocatalyst for degradation of methylene blue and congo red

Photocatalytic degradation of organic dyes using novel metal based composite materials is one of the most intriguing and sustainable ways to reduce water pollution. Herein, facile synthesis of AgNPs@ZIF-8 via in situ generation of AgNPs and ZIF-8 (Zeolitic Imidazolate Framework) was demonstrated, and composites with different Ag contents (abbreviated as SZ, SZ1, SZ2 SZ3) were well characterized by powder X-ray diffraction (PXRD) pattern, X-ray photoelectron spectroscopy (XPS) and Fourier transform infra-red (FT-IR) spectroscopy. Encapsulation/decoration of AgNPs (particle size: 96 nm in SZ and 17.32 +/- 2.35 nm in SZ1 to SZ3) in ZIF-8 matrix has been ensured by TEM and EDX analysis. Brunauer-Emmett-Teller (BET) adsorption-desorption studies indicate that the surface area of SZ (982 m(2) g(-1)) is less than those of SZ1 to SZ3 (due to the encapsulation of large amount of Ag nanoparticles in SZ). The synthesized composites are thermally stable up to 400 degrees C in air and nitrogen atmosphere. AgNPs@ZIF-8 exhibited excellent photocatalytic efficiency to degrade organic dyes compared to ZIF-8 due to its large surface area, highly porous and unique synergistic properties. SZ2 degrades off 97.25 % methylene blue (MB) and 100 % congo red (CR) at pH >= 7. Further, degraded fragments were analysed by GC-MS and plausible degradation mechanism was discussed.